1. Field of the Invention
The present invention relates generally to a head slider which can be incorporated in a disc drive such as a magnetic or optical disc drive. More particularly, the present invention relates to a low-flying type head slider provided on an air bearing surface thereof with a plurality of pads for preventing adhesion of the surface onto a disk surface.
2. Description of the Related Art
In the field of a magnetic disk drive provided with a flying magnetic head system, the flying height of a magnetic head slider has been significantly reduced to improve a packing density of a magnetic recording medium or disk and to downsize the disk drive. As the flying height is reduced, the surface of a magnetic disk must be highly smoothed to avoid a contact between the magnetic head slider and the rotating magnetic disk. In a contact-start-stop (CSS) type magnetic disk drive, however, when the smoothness of the surface of a magnetic disk is improved, a magnetic head slider is likely to adhere to the magnetic disk during the rest condition of the disk, and the normal operation of the magnetic disk drive may be hampered.
To solve the problems of adhesion of the head slider, an adhesion-free slider structure and a zone-textured medium structure has been known. In the adhesion-free slider structure, an air bearing surface (ABS) formed in the head slider for generating flying force is provided with a plurality of pads projecting from the ABS to prevent the adhesion of the latter. In the zone-textured medium structure, a CSS zone in the surface of the magnetic disk, on which the head slider is put during the rest condition of the disk, is locally roughened. These structures are provided to reduce a contact area of the ABS of the magnetic head slider with the surface of the magnetic disk, so as to minimize adhesion or friction force therebetween.
In the conventional magnetic head slider, it is also known that a tapered surface is formed adjacent to the air introducing end of the ABS to allow air to flow onto the ABS, to establish easy and quick flying of the disk when the disk starts to rotate. If the above adhesion-free slider structure is applied to such a magnetic head slider with the tapered surface, the head slider is likely to generate a pitching motion of the slider body in an initial flying stage of the head slider just after the disk starts to rotate. When the magnetic head slider generates pitching, a mutual joint or transit portion between the ABS and the tapered surface is repeatedly brought into contact with the surface of the magnetic disk and is soiled by dust such as powdered materials produced by abrasion. As a result, the reliability of a head-disk interface (HDI) may be deteriorated.
From this view point, the solution has been to form adhesion preventing pads on the magnetic head slider with the tapered surface, wherein at least one pad is formed near the air introducing end so as to extend across the mutual joint or transit portion between the ABS and the tapered surface (see, e.g., Japanese Unexamined Patent Publication (Kokai) No. 9-293223 (JP-A-9-293223)). In this structure, the pad near the air introducing end comes into contact with the magnetic disk surface during the pitching of the magnetic head slider in the initial flying stage thereof, and thereby serves to prevent the joint portion from being soiled due to the contact with the magnetic disk surface.
In the magnetic head slider having the tapered surface provided adjacent to the air introducing end, the tapered surface is normally formed by a machining process, such as grinding, prior to the formation of the ABS on the slider body by, e.g., an ion milling or ion beam etching process. In this occasion, the machined tapered surface tends to have a relatively large dimensional tolerance, in the direction of an air flow and essentially due to the machining process, in the order of dozens of percent of the reference dimension of the tapered surface in the air flow direction. Then, the adhesion preventing pads described above are formed by, e.g., an ion milling or ion beam etching process at a desired position on the machined tapered surface and a surface portion where the ABS is formed at a later stage, after forming the tapered surface and before forming the ABS.
In the adhesion-free slider structure, when a total contact surface area of the adhesion preventing pads with the magnetic disk is reduced, the adhesion or friction force caused between the slider and the disk is lowered according thereto. In this situation, the mutual joint or transit portion between the ABS and the tapered surface tends to have a positional deviation due to the dimensional tolerance caused by the machining process for the tapered surface. On the other hand, the adhesion preventing pads are formed generally accurately at predetermined positions on the surface of the head slider, and the positional deviation of each pad is relatively small. Accordingly, when the adhesion preventing pads are formed, the surface of the pad near the air introducing end, extending across the joint portion, is provided with a surface part generally parallel to the ABS and having the adhesion preventing effect, and the surface area of the surface part may fluctuate.
As a result, the total contact area of the adhesion preventing pads with the magnetic disk may fluctuate, and thereby the adhesion force is uneven between the slider and the disk. That is, even if the adhesion preventing pads are accurately formed at the predetermined positions, the total contact area of the adhesion preventing pads with the magnetic disk is increased according to the reduction of the dimension of the machined tapered surface, which results in an increase in the adhesion force and thus may disturb the normal operation of the magnetic disk drive.
It is therefore an object of the present invention to provide a head slider, of a low-flying type, which can solve the above-mentioned problems and thus can improve the performance of a disk drive.
It is another object of the present invention to provide a low-flying type head slider, adopting an adhesion-free slider structure, which can eliminate or at least minimize the unevenness of the adhesion force between the slider and a disk, and also can prevent the mutual joint or transit portion between the ABS and the tapered surface from being soiled.
It is further object of the present invention to provide a disk drive incorporating therein an improved head slider to realize a large capacity and high density performance.
In accordance with the present invention, there is provided a head slider comprising a slider body provided with an air bearing surface arranged in one surface of the slider body and a tapered surface arranged adjacent to an air introducing end of the air bearing surface; at least one first pad formed on and projecting from the air bearing surface, the at least one first pad being located close to a joint portion between the air bearing surface and the tapered surface; and at least one second pad formed on and projecting from the tapered surface, the at least one second pad being located close to the joint portion and away from the at least one first pad.
In a preferred aspect of the invention, the first pad is spaced from the joint portion.
Also, in a preferred aspect of the invention, the second pad is spaced from the joint portion.
It is preferred that a distance between the first pad and the second pad in an air flow direction is determined to be at least twice a dimensional tolerance, in the air flow direction, of the tapered surface.
In this arrangement, the dimensional tolerance may be 10% to 30% of a reference size, in the air flow direction, of the tapered surface.
Plural first pads may be arranged opposite to respective plural second pads in relation to the joint portion.
The head slider may further comprise at least one third pad formed on and projecting from the air bearing surface and the tapered surface, the at least one third pad extending across the joint portion.
The at least one first pad may be disposed on one side of the slider body in relation to the air flow direction.
In this arrangement, the at least one second pad may be disposed on one side of the slider body in relation to the air flow direction.
The present invention also provides a disk drive comprising the head slider mentioned above.
The disk drive may further comprise a disk provided with a locally roughened region on a surface of the disk, wherein another side opposite to the one side of the slider body of the head slider is positioned nearer the locally roughened region than the one side.
The present invention further provides a head slider comprising a slider body provided with an air bearing surface arranged in one surface of the slider body and a tapered surface arranged adjacent to an air introducing end of the air bearing surface; and at least one pad formed on and projecting from the air bearing surface, the at least one pad being located close to a joint portion between the air bearing surface and the tapered surface and outside of the tapered surface even when the tapered surface has a dimension, in an air flow direction, of the maximum limit of size.